Self-effacing is not self-denial. The gist of the traditional Chinese culture is the idea of "Being modest makes you progress while being proud make you regress."
The translation - "not at all" has made the gist or implication lost and thus is much worse than "Where? Where?", which is a modest way or a humble gesture to show the gratitude in heart (because the speaker is delighted to hear it) - That is, Chinese says "Thank you" in heart while English says "Thank you" in both mouth and heart.
The phrase "Where? Where?" reflects in a colloquial way the happy medium (中庸之道). The Happy Medium is at the core of traditional Chinese culture or Confucianism. It refuses going to extremes and thus the translation "not at all", which has gone to extremes, is a bust.
It appears not transferable if limited to a few words. So far "Where? Where?" is one of the best, compromised though, translations because the uncertainty that the phrase shows trickily induces your good wishes.